Treatment that stops or slows the growth of blood-forming cells in the bone marrow. Myelosuppressive therapies, such as chemotherapy and radiation therapy, kill normal cells and cancer cells in the bone marrow. This lowers the number of normal red blood cells, white blood cells, and platelets in the blood and bone marrow. Myelosuppressive therapy may be given before a bone marrow or stem cell transplant. It may also be used to treat some blood conditions, such as polycythemia vera (a disease in which there are too many red blood cells in the bone marrow and blood).